This invention lies in the field of folding knives with mechanisms to secure blades in position. In particular, this invention is directed to a release mechanism for folding blades which are secured in an open position.
Lock back systems have been in use for many years. In a typical lock back folding knife, as a blade is extended or opened, a follower rides along the edge of a cam on the tang of the blade and drops into a notch complementary to the follower. A spring holds the follower in the notch and secures the blade in the open position. In order to close the blade the lock must be released. Conventional release mechanisms provide means for vertically displacing the follower out of the notch. Examples of such knives have been disclosed by Johnson in U.S. Pat. No. 4,040181 and Sawby et. al. in U.S. Pat. No. 4,240,201.
In 1884, in British patent No. 9352 for an automatic pocketknife, Haddan disclosed a mechanism for closing a pocketknife in which a follower was laterally displaced into a groove on the cam of a blade. In Haddan, the follower is part of a locking arm or spring that is under tension. The tension applies a rotational force, or torque, along the edge of the cam to automatically open the blade.